1. Field of the Invention
The present invention relates to a method of manufacturing a plastic pipe, the wall of which comprises longitudinally extending hollow channels, by extruding a thermoplastic through an annular extrusion zone provided with longitudinal closed zones, which form the hollow channels whereby, prior to approaching said longitudinal closed zones, the stream of thermoplastic is subdivided into two concentric annular streams, the stream of thermoplastic being subdivided at at least one location into ring segment partial streams.
2. Description of the Prior Art
In the prior art a method for manufacturing a plastic pipe, the wall of which comprises longitudinally extending hollow channels, has been used. In said prior art method the stream of thermoplastic is, prior to approaching the longitudinal closed zones, subdivided into two concentric annular streams, whereby each of said streams of thermoplastic is in turn subdivided into a ring segment partial stream.
This prior art method is inconvenient as problems will occur when plastic pipes of the aforementioned type, having a very small diameter, have to be produced. The construction of the apparatus concerned will also involve many problems, as a suspension of the device which serves for the subdivision of the stream of plastic into two concentric annular streams is rather difficult and complicated.